JPH06263042A - Motor-driven power steering control device - Google Patents

Abstract

PURPOSE:To prevent misjudgment of a trouble caused by noise and the like by reducing influence of the trouble upon torque sensors, and lengthening a trouble judging period. CONSTITUTION:Torque sensors 3a and 3b detect steering torque of a steering system. An amplifying circuit 901 amplifies output of the torque sensor 3a, and an amplifying means 902 amplifies output of the torque sensor 3b. An average value calculating means 903 finds an average value of the outputs of the amplifying circuit 901 and the amplifying means 902. A torque difference detecting means 906 compares the outputs of the sensors 3a and 3b with each other, and detects a difference. A torque selecting means 904 selects the output of the amplifying circuit 901 when the difference is within a constant value, and selects the output of the average value calculating means 903 when it exceeds the constant value. A phase compensating element calculating means 905 calculates a phase compensating element according to output of the torque selecting means 904, and an electric current calculating driving means 909 controls a driving current of a motor 13 to assist steering torque according to this calculated value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering controller, and more particularly to an electric power steering controller having a fail-safe function when a torque sensor fails.

[0002]

2. Description of the Related Art Conventionally, various electric power steering control devices have been proposed which detect a steering torque of a steering system, control a drive current of an electric motor according to the detected steering torque, and assist the steering torque. Has been done.

(A) For example, two torque sensors for detecting the steering torque of the steering system are provided, and assist control of the steering torque is performed according to the output of one of the torque sensors.
When the outputs of both torque sensors are compared and if the difference exceeds a certain value, it is judged that the torque sensor has failed and the assist control is stopped to provide a fail-safe function when the torque sensor fails. (Actual exploitation 62-152
880).

(B) Further, for example, there is one in which a plurality of torque sensors for detecting the steering torque of the steering system are provided, and assist control of the steering torque is performed according to the low level value of the outputs of these torque sensors. In such a power steering control device, when a certain torque sensor fails, the assist control is always performed so that the assist torque becomes low.

[0005]

Since the conventional electric power steering control device is constructed as described above,
There were the following problems. Regarding (a), if one torque sensor fails and the difference between the outputs of both torque sensors becomes a certain value or more, if the time for failure determination is long, the steering torque assist control during that time is executed. If a shock is generated in the steering system, and conversely the time for failure determination is short, the steering torque will be erroneously determined to be a failure when noise or the like is temporarily mixed in the output of one torque sensor. There was a problem that the assist control of was stopped.

With regard to (b), for example, when the output of the faulty torque sensor becomes a low level, the assist torque is lowered so that the assist torque is actually higher while the assist torque is lower. There was a problem that it was controlled and the influence of the failure was large.

The present invention has been made in order to solve such a problem, and reduces the influence of a failure of the torque sensor and prevents an erroneous determination of the failure due to noise or the like. The purpose is to provide.

[0008]

An electric power steering control device according to the present invention includes a plurality of torque sensors for detecting steering torque of a steering system of a vehicle, and an output of one of the plurality of torque sensors. An average value calculating means for obtaining an average value of outputs of other torque sensors, a torque difference detecting means for comparing outputs of a plurality of torque sensors to detect a difference, and a driving current of a motor for assisting the steering torque to detect a torque difference. When the difference detected by the means is within a fixed value, control is performed according to the output of one torque sensor, and when the difference exceeds the fixed value, control means is controlled according to the output of the average value calculation means. Be prepared.

[0009]

According to the present invention, when a certain torque sensor out of a plurality of torque sensors fails and its output level shifts to the higher or lower side, assist control is performed according to the average value of the outputs of the plurality of torque sensors. Therefore, the influence of the failure can be reduced. Further, since the influence of the failure is reduced, even if the failure determination time is lengthened, the shock generated in the steering system is small. Therefore, it is possible to lengthen the failure determination time and prevent erroneous determination of the failure due to noise or the like. Become.

[0010]

【Example】

Example 1. An embodiment of an electric power steering control device according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, 1 is a steering wheel which receives a steering torque of a driver, and 3a and 3b are first and second torque sensors which output an electric signal according to the torque applied to the steering wheel 1, respectively. Detect the torque.

4a is a first universal joint, 4
b is the second universal joint, 2a is the handle 1
And a torque sensor 3a, 3b between the first steering shaft, 2b is a second steering shaft connecting the torque sensor 3a, 3b and the first universal joint 4a, 2c is a universal joint 4a,
It is a steering shaft which connects between 4b.

Reference numeral 5 is a first pinion shaft connected to the second universal joint 4b, and 6 is a first pinion shaft 5.
The first rack tooth portion 6a and the second rack tooth portion 6 that mesh with
b is a rack shaft, 7a is a ball joint that connects the tie rod 8a and one end of the rack shaft 6, and 7b is a ball joint that connects the tie rod 8b and the other end of the rack shaft 6.

Reference numeral 9 is a control unit having a microcomputer, 10 is a vehicle speed sensor for detecting the vehicle speed, 11 is an on-vehicle battery, 12 is a key switch, 1
A DC motor 3 is supplied with power from the battery 11 via the control unit 9. 14 is a motor 13
An electromagnetic clutch that is driven by being directly connected to the output shaft of 15 is a worm shaft that forms a speed reducer that is connected to the output shaft of the electromagnetic clutch 14, 16 is a worm wheel shaft that is driven by meshing with the worm shaft 15, and 18 is a worm wheel shaft. Worm wheel shaft 1
6 and the second rack tooth portion 6b of the rack shaft 6 are engaged with each other.
It is the pinion axis.

FIG. 2 shows a specific structure of the control unit 9. In the figure, 901 is the torque sensor 3
The steering torque amplification circuit that amplifies the output of a by n times by hardware, 902 is the steering torque amplification means that amplifies the output of the torque sensor 3b by n times by software, and 903 is the output of the steering torque amplification circuit 901 and the steering torque amplification. Means 90
The steering torque average value calculating means for calculating the average value of the outputs of 2 and 906 is the steering torque difference detecting means for detecting the difference of the outputs of the torque sensors 3a and 3b.

Reference numeral 904 is a steering torque selection means for selecting one of the output of the steering torque amplification circuit 901 and the output of the steering torque average value calculation means 903 according to the output of the steering torque difference detection means 906, and 905 is a steering torque selection means 904.
Phase compensation element calculation means for calculating the phase compensation element from the output of the vehicle speed, 907 is a timer (error counter) that operates according to the output of the steering torque difference detection means 906, and 908 is a vehicle speed measurement for measuring the vehicle speed from the output of the vehicle speed sensor 10. It is a means.

Reference numeral 911 is motor current measuring means for measuring the current of the motor 13, and 912 is motor voltage measuring means for measuring the voltage of the motor 13. Reference numeral 909 is a current calculation drive means for calculating the current of the motor 13 from the phase compensation element calculation means 905, the vehicle speed measurement means 908, the timer 907 and the motor current measurement means 911, and the current calculation drive means 910 for driving the motor 13 to have the current value. Phase compensation element calculation means 905,
The vehicle speed measuring means 908, the timer 907, and the motor voltage measuring means 912 determine whether the clutch 14 is on or off,
It is a clutch on / off determination control means for controlling the clutch 14. Note that the components 904, 905 and 909
Constitutes a control means. In addition, here, the component 90
Although 1 is a hardware configuration, components 902 to 91
2 is substantially a software configuration.

FIG. 3 is a flow chart showing the assist control of the microcomputer constituting the control unit 9. In step S1, the output T1 of the torque sensor 3a is taken in, and in step S2, the steering torque amplifier circuit 9
The output T1 'of 01 is fetched, and the output T2 of the torque sensor 3b is fetched in step S3. In both cases, these data are stored in the memory (not shown).

Next, in step S4, the output T from the memory is output.
1 and T2 are read, and these are in the normal range (T
_{(Between MIN} and T _MAX ). If it is not within the normal range, an error counter (timer 90
7) is counted up, and it is determined in step S6 whether or not the time is over. If the time is over, it is determined that the torque sensor has failed, and in step S7 the current supply to the motor 13 is stopped, the clutch 14 is turned off, and the assist control is stopped.

Next, if the time is not over at step S6, the output T2 of the torque sensor 3b is amplified to obtain the output T2 'at step S8, which is stored in the memory. Then, in step S9, the output T1 'and the output T2' are read out, the average value of them is obtained, and the control torque is set as the control torque T.

If it is within the normal range in step S4, the absolute value of the difference between the output T1 and the output T2 is a constant value ΔT in step S10.
It is determined whether or not the following. If the absolute value of the difference is less than or equal to ΔT, it is normal and the error counter is cleared in step S11. The output T1 ′ is set as the control torque T in step S12, and the process proceeds to step S13. If the absolute value of the difference is not less than ΔT in step S10, the process proceeds to step S5.

In step S13, the phase compensation element is calculated from the control torque T, and in step S14, the vehicle speed is calculated. Then, in step 15, the motor assist current is calculated according to the phase compensation element and the vehicle speed, and the motor 13 is driven so that the motor current becomes the calculated current, and step S1
Return to.

Thus, in this embodiment, the drive current of the DC motor 13 for assisting the steering torque is normal when the difference between the outputs of the torque sensors 3a and 3b is within a certain value, that is, both torque sensors are normal. When the difference exceeds a certain value, that is, when one of the torque sensors fails, control is performed according to the average value of the amplified outputs of both torque sensors. Therefore, the DC motor 13 with respect to the change of the control torque is
It is possible to reduce the amount of change in the drive current of
Even if the torque sensor fails in any manner, the assist control can always be performed on the safe side, and erroneous determination of failure due to noise or the like can be prevented.

Example 2. In the above embodiment,
Although two torque sensors 3a and 3b are provided,
It is also possible to provide three or more torque sensors and to similarly configure.

[0024]

As described above, according to the present invention, a plurality of torque sensors for detecting the steering torque of the steering system of the vehicle,
An average value calculating means for obtaining an average value of the output of one torque sensor and the output of another torque sensor among the plurality of torque sensors, and a torque difference detecting means for comparing the outputs of the plurality of torque sensors to detect a difference, The drive current of the motor that assists the steering torque is controlled according to the output of one torque sensor when the difference detected by the torque difference detection means is within a certain value, and is averaged when the difference exceeds the certain value. When a torque sensor out of a plurality of torque sensors fails and the output level shifts to the higher or lower side, a plurality of torques are provided. Since the assist control is performed according to the average value of the sensor output, the influence of failure can be reduced,
Further, even if the failure determination time is lengthened, the shock generated in the steering system is small. Therefore, the failure determination time can be lengthened to prevent erroneous determination of a failure due to noise or the like. Since only one is required, there is an effect that it becomes cheaper.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an electric power steering control device according to the present invention.

FIG. 2 is a configuration diagram showing a specific configuration of a control unit in one embodiment of the electric power steering control device according to the present invention.

FIG. 3 is a flowchart showing an operation example of assist control of an embodiment of the electric power steering controller according to the present invention.

[Explanation of symbols]

 1 steering wheel 3a, 3b torque sensor 9 control unit 10 vehicle speed sensor 13 direct current motor 903 steering torque average value calculation means 904 steering torque selection means 905 phase compensation element calculation means 906 steering torque difference detection means 909 current calculation drive means

Claims (1)

[Claims] 1. A plurality of torque sensors for detecting steering torque of a steering system of a vehicle, and an average value calculating means for obtaining an average value of outputs of one torque sensor and another torque sensor of the plurality of torque sensors. And a torque difference detecting means for comparing the outputs of the plurality of torque sensors to detect a difference, and a drive current of the motor for assisting the steering torque within a constant value of the difference detected by the torque difference detecting means. In some cases, control means is provided according to the output of the one torque sensor, and when the difference exceeds the certain value, control means is provided in accordance with the output of the average value calculating means. Electric power steering control device.